For concatenation of dataset DCB parameter should be same( Logical record length should be same). All data sets concatenated must be of the same type . If I am wrong pls correct me .

Your are partially correct nutan. All the datasets need to be of same data type(DSORG should be same). But as I have said before, they can have different logical record lengths. The only constraint is that the dataset with the largest record length must be given first.